I heard of a collie greyhound like that. Hated foxes with a passion and served its owner well, fed and kept in coin. I never saw it run either. but apparently its offspring were equally superb. Cant remember the guys name, but the dog was called Merle.
Sounds like the start of dynasty there....
I think they did breed off this dog but like his owner said once in a lifetime never heard of the offspring being spoke about like this dog